The present invention relates to a new and improved method for the fabrication of a mixture from a highly-viscous liquid phase and a thermoplastic and/or elastomeric material, and further pertains to an apparatus for the performance of the aforesaid method and to the use of the method for the fabrication of mixtures of bitumen or tar and a thermoplastic or elastomeric material.
In many fields there is the requirement of fabricating a mixture of a highly-viscous liquid phase and a thermoplastic material. The procedures which are employed in such instances can influence, apart from the economies, also decisively the properties of the product. Under favorable circumstances such effects in practice can lead to failure in realizing the theoretically possible advancements. An example of this is the fabrication of sheets or webs for covering roofs and the use of a mixture of bitumen and a thermoplastic or elastomeric material. Such mixtures have become known in more recent times, and it has been found that, in contrast to bitumen (without the mentioned mixture components) especially when employed in conjunction with roofing pasteboards and the like, they possess outstanding properties. These properties particularly come into play during the laying of the roof and with respect to the quality and longevity of the roofing coating or covering, especially also, but not exclusively, in the fact that the inherent properties of the bitumen and which are disadvantageous in this environment of use, can be overcome. Up to the present there was not available any technique which enabled fabricating the required quantities of such mixtures in a relatively short period of time as needed for the application thereof to the carrier web, without there either being present an impermissible expenditure in equipment and/or impairment of the material properties.
Mixtures of the previously mentioned type were heretofore fabricated, for instance, in extruders, calenders, kneaders, Banbury-mixers and the like. Starting with solid or solid and liquid phases, the material was mechanically processed in such equipment in narrow gaps, with the result that localized plasticizing and mixing occurred. As a result, there could occur mechanical decomposition of the plastic and synthetic rubber, but also undesired depolymerization because of localized overheating. Furthermore, the output, in relation to the considerable expenditure in equipment, is relatively small, especially when it is considered that the mixture is supplied to a high-speed roofing pasteboard or coating installation.
Mixtures of the type under consideration also can be fabricated in slowly operating stirrers wherein, for instance, a liquid phase is admixed with a solid phase or a different liquid phase and brought into a state of solution. As a result, it is possible to process large charges or batches, but still the mixing operation must be carried out over a considerably long time-span at high temperatures, so that for instance plastic constituents are subjected to thermal decomposition, with the result that the exceptional properties attributable to such mixture components like plasticity, elasticity, aging resistance and the like, are destroyed. Since such mixtures are further processed at elevated temperatures and the thermal decomposition, depending upon the composition of the materials, already can occur after a relatively short period of time, the long fabrication times requires particular speed during the further processing, for instance during casting or application to the carrier webs, since otherwise the impairment in the properties during use can be promoted or can occur in any case. Hence, for supplying high-speed operating roofing pasteboard installations and the like, these proposals have been found to be unsuitable.